1. Field of the Invention
This invention relates to resolving conflicting topology information in a communication network. More particularly, the invention relates to a topology manager that is separate from the network, has agents in the network, collects topology information from the agents and resolves conflicting topology information.
2. Description of Prior Art
In a data communication network, nodes participating in communication share network topology information. The accuracy of the topology information is guaranteed by using self-correcting sequence numbers to resolve conflicting topology information. However, this requires that the node participate in both receiving and sending network information to other nodes.
A problem arises when a computer application program, acting as a network topology manager, does not reside on a communication node that can send network topology information to correct topology information inconsistencies. Today, a topology manager application may not even be a part of the network. In such a situation, the topology manager is relying on an agent application program to forward topology information about the network. This is especially common where a vendor is providing management services to a network, but does not participate in normal data exchange on the network.
Inconsistent information arises in a network when a network becomes fragmented. Some nodes in the fragmented network can no longer exchange topology information with other nodes. Each node retains all of its topology information, even though some of the information may no longer be reliable. When the network reconnects, each node only needs to be informed of updates that happened while fragmented rather than relearning the entire topology of the network.
When a topology manager is not on a node that participates in sending topology information, or is not in the network at all, during fragmentation the manager may receive topology information from each subnetwork formed by the fragmentation. The problem for the manager is to determine what topology information from each subnetwork is reliable.
The following United States patents are exemplary of the topology management from within the network: U.S. Pat. No. 4,718,005 entitled "Distributed Control of Alias Name Usage in Networks;" U.S. Pat. No. 4,827,411 entitled "Method of Maintaining a Topology Database;" U.S. Pat. No. 4,644,532 entitled "Automatic Update of Topology in a Hybrid Network;" U.S. Pat. No. 5,049,873 entitled "Communication Network State and Topology Monitor;" U.S. Pat. No. 5,109,483 entitled "Node Initiating XID Exchanges Over an Activated Link Including an Exchange of Sets of Binding Signals Between Nodes for Establishing Sessions;" and U.S. Pat. No. 5,218,676 entitled "Dynamic Routing System for a Multinode Communications Network." Since the topology management is within the network in these patents, they do not have the problem described above and addressed by the present invention.